Zoom lens on an SLR camera
A zoom single-lens reflex is a modified lens system that allows the photographer to view his subject through the same lens used to take the picture. It also allows a photographer to magnify the subject at a distance (zoom). The first zoom lenses were patented by Clile C. Allen in 1902, and later manufactured by Bell and Howel Cooke in 1932. The first SLR lenses were created in the 1880's. There is some debate over whose SLR design was first marketed, C.R. Smith or Thomas Sutton.
Before the invention of the SLR's, cameras employed viewfinders; but that created parallax problems (the line of site leading to the viewfinder is different from that leading to the lens). The result is a picture framed differently from that seen through the viewfinder.
Instructions
Understand and Use an SLR Camera with Zoom Lens
1. Zoom lenses are made up of elements (many individual lenses that work together). As one group of lenses move, another group corrects for the change in focal length. The result is a controllable range of magnification. But for all things good, comes a cost; because many lenses work together aberrations (light distortions) are created. Improved lens technology has eliminated a lot of the distortion but some still persist. Zoom is accomplished by rotating the base of the lens.
2. Learn the functions of the zoom lens. The lens works with the camera to control zoom, focus, aperture and exposure. These are the major components of creating photographs.
The mechanisms that control aperture and exposure reside in the lens and communicate with the body of the camera. Mastery of aperture, exposure, focus and framing lead to effective photography.
3. Set the aperture. The aperture of the lens controls the diameter of its opening to the camera. It controls the amount of light that enters the camera and strikes the CCD (digital sensor) or film. The smaller the diameter the more in-focus the entire field of view becomes. The greater the diameter the smaller the field of focus is, resulting in pictures with sharp subjects and blurry surroundings. Aperture is measured by f-stops; the greater the f-stop the smaller the diameter of the opening. In dark environments large apertures may be used to increase the light entering the camera. Standard aperture settings, large to small, include 1.0, 1.4, 2.0, 2.8, 4, 5.6, 8, 11, 16 and 22.
4. Set the desired exposure. Exposure is the length of time the shutter remains open while capturing an image. It is directly related to aperture; the smaller the aperture, the less light enters the camera, the longer the exposure needs to be. Exposure times are presented in terms of seconds or fractions of a second. Action scenes require very fast shutter speeds to freeze the motion, while slow moving objects in dark environments can have long exposures.
5. Understand reciprocity: the change in light between each increasing f-stop is half, so the exposure times need to be doubled to create the same image.
6. Focus on the subject by rotating the tip of the lens. Many camera lenses are fitted with an auto-focus option, thus relieving the photographer of a repetitive task.
7. Set the camera to automatic if desired. Most SLR's are equipped with a full auto-function that provides focus, exposure and aperture. Also, most SLR's are equipped with an aperture priority setting (manual input of aperture) and an exposure priority setting (manual input of exposure time). The complimentary components are calculated by the camera's light sensing computer.
8. Take the picture and enjoy.
Tags: aperture exposure, allows photographer, dark environments, diameter opening, enters camera
